Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$99.49	4.373%	$103.8407	$103.84	$103.85	$103.80
Purchase #2	$150.47	11.233%	$167.3723	$167.37	$167.35	$167.40
Purchase #3	$161.30	11.741%	$180.2382	$180.24	$180.25	$180.20
Purchase #4	$186.76	12.500%	$210.105	$210.11	$210.10	$210.10
Purchase #5	$82.37	8.517%	$89.3855	$89.39	$89.40	$89.40
Purchase #6	$48.87	11.295%	$54.3899	$54.39	$54.40	$54.40
Purchase #7	$61.66	9.605%	$67.5824	$67.58	$67.60	$67.60
7 purchase totals =	$790.92		$872.9140	$872.92	$872.95	$872.90